1. Field of the Invention
The present invention relates to process and equipment for recovering a developer from a photoresist development waste and reusing it, and particularly to process and equipment for recovering a developer from a photoresist development waste, discharged from a process of producing electronic parts such as semiconductor devices (LSI, VLSI, etc.), liquid crystal displays (LCD) or printed boards, or the like, and reusing it.
2. Related Art
In the field of manufacturing electronic parts such as semiconductor devices and liquid crystal displays, and the like, integration scale-up and miniaturization of products have been in rapid progress. For example, the procedure of manufacturing such electronic parts includes a photolithographic process, wherein a photoresist film is formed on a substrate such as a wafer or a glass substrate, predetermined parts of the film are then irradiated with a light or the like, and subsequently the photoresist film is developed with a developer to form a fine pattern. Herein, photoresists include positive photoresists that turn soluble in a developer where exposed to a light or the like, and negative photoresists that turn insoluble in a developer where exposed to a light or the like. In the field of manufacturing electronic parts such as semiconductor devices and liquid crystal displays, positive photoresists are predominantly used. An aqueous solution of a tetraalkylammonium hydroxide (hereinafter often referred to in brief as "TAAH") such as tetramethylammonium hydroxide (hereinafter often referred to in brief as "TMAH") or trimethyl(2-hydroxyethyl)ammonium hydroxide (i.e., choline) as an organic alkali is usually used as a developer for such positive photoresists. Incidentally, although the mainstream developers for the negative photoresists are organic solvent developers, alkali developers may also be used for some negative photoresists.
A photoresist as material to be developed is a hydrophobic substance, and an aqueous solution of TAAH such as TMAH is hydrophilic, whereby the interfacial affinity therebetween is poor. Because of the poor interfacial affinity of the aqueous TAAH solution for the photoresist, effective development of fine patterns is difficult with the aqueous TAAH solution as an ordinary alkali developer. In order to solve this problem, alkali developers containing a surfactant have already been marketed and put into practical use (e.g., developer commercially available under the trade name of "NMD-W" and manufactured by Tokyo Ohka Kogyo Co., Ltd.).
Meanwhile, waste discharged from the development step of using an aqueous TAAH solution as the alkali developer in the photolithographic process (called "photoresist development waste" and hereinafter often referred to in brief as "development waste") usually contains the dissolved photoresist and TAAH, and is hard to render harmless through any treatments. Thus, it is desired to recover and reuse TAAH because of its adverse effects on environment, and various attempts have been made to develop a method of recovering and rejuvenating an alkali developer (hereinafter often referred to as "developer"). Examples of such a method include methods comprising electrodialysis or electrolysis (Japanese Patent Laid-Open No. 7-328642 published on Dec. 19, 1995, and Japanese Patent Laid-Open No. 5-17889 published on Jan. 26, 1993), a method using an anion exchange resin (Japanese Patent Laid-Open No. 10-85741 published on Apr. 7, 1998), a method comprising electrodialysis or electrolysis and using an ion exchange resin(s) (U.S. Patent No. 5,874,204 patented on Feb. 23, 1999), a method comprising neutralization and electrolysis (Japanese Patent Laid-Open No. 7-41979 published on Feb. 10, 1995), a method using activated carbon (Japanese Patent Laid-Open No. 58-30753 published on Feb. 23, 1983), and a method using a nanofiltration membrane (NF membrane) [Japanese Patent Laid-Open No. 11-192481 published on Jul. 21, 1999].
Since TAAH-containing developers recovered by these methods contain no substantial surface-active substances, however, they are highly hydrophilic solutions. Even where a surfactant is contained in a virgin developer, the recovered TAAH-containing developer has a decreased surfactant concentration, which makes it difficult to secure a surface-active effect comparable to that of the virgin developer, thereby posing a problem that it cannot be reused as a developer in the same development step as it is.
Accordingly, an object of the present invention is to provide process and equipment for recovering a developer from a photoresist development waste and reusing it, which can give a rejuvenated developer capable of stably and effectively developing fine patterns of a photoresist by proper adjustment and control of the surface-active effect (wetting properties) of a TAAH-containing solution recovered from the development waste.